We recently proposed that the presence of a low lying covalent "1Ag"-like excited state in 11-cis retinal could account for a number of the molecule's anomalous photophysical properties (R.R. Birge, K. Schulten and M. Karplus, Chem. Phys. Letters. 31, 451 (1975)). Despite this state's potential importance, however, no one has yet reported its direct experimental observation in 11-cis retinal or any of the other retinyl polyenes. The purpose of the proposed research is to use two photon tunable dye laser spectroscopy and resonance Raman tunable dye laser excitation profile spectroscopy to identify in the visual chromophores the energy and photophysical characteristics of the "1Ag*"-like state, as well as other "forbidden" pi pi* and sigma pi* states. Solvent effect studies of the excitation bands obtained by both methods will be used to help characterize the dipolar and dispersive properties of the observed electronic states. This information will be compared with the results of all valence electron SCF-MO-CID calculations optmized by the inclusion of high levels of double excitation configuration interaction. A portion of the research effort will be devoted to the development of a useful semiempirical all valence electron SCF-MO-CID formalism. The molecules to be spectroscopically and theoretically studied will include the all-trans, 9-cis, 11-cis and 13-cis isomers of retinol, retinal, the Schiff base of retinal and the protonated Schiff base of retinal as well as the visual pigment, rhodopsin. Since both of the proposed spectroscopic methods are subject to functional and interpretive complications, a comparison of their diagnostic potential in the study of "forbidden" excited states will help characterize the general utility of these methods as well as help guard against incorrect assignments by frequently providing a "double check" on observed spectral features. This investigation will afford the first detailed analysis of the location and conformational dependence of the low-lying "forbidden" levels in these compounds, and will help delineate their importance in the visual process.